Postprandial triacyglycerol in response to dietary fat
This thesis is an investigation of postprandial triacylglycerol (TAG) metabolism in men using a newly designed oral fat tolerance test (OFTT) consisting solely of emulsified lipids that was developed to evaluate the effect of specific ratios of polyunsaturated/saturated (P/S) fatty acids. As the postprandial response to dietary fat has been described as inflammatory, several key inflammatory mediators were also investigated in this thesis. In chapter 3, an OFTT was developed and used to evaluate the postprandial response to two OFTTs (P/S 0.2, 2.0) in 8 men. Postprandial TAG increased (P<0.05) to a similar degree in both trials. Importantly, postprandial glucose and insulin decreased (P<0.05) following the OFTT, indicative of the pure fat nature of the OFTT. These data demonstrate that the OFTT allows for the evaluation of the postprandial response to fat alone. In chapter 4, the postprandial response was investigated in 8 men with low (LTAG, TAG <= l.69 mmol/L) and 8 men with high (HTAG, TAG>=1.7 mmol/L) fasting TAG who underwent three OFTTs (P/S 0.2, 1.0 and 2.0). Overall, P/S ratio had no effect on postprandial measurements. HTAG men demonstrated an exaggerated postprandial TAG response (P<0.05). HTAG men also had greater postprandial plasma interleukin (IL)-6 (P<0.05), an important inflammatory marker that is secreted from adipose tissue and is elevated in obesity. These data demonstrated that in addition to elevated fasting TAG, HTAG men have exaggerated postprandial TAG and an increased postprandial inflammatory profile in response to dietary fat alone. In chapter 5, the effect of one bout of exercise 16h prior to an OFTT was evaluated in 9 hypertriacyglycerolemic men (fasting TAG>2.0mmol/L). Prior exercise decreased fasting and postprandial very-low density lipoprotein TAG (P<0.05), while chylomicron TAG was not changed. Plasma IL-6 and gut hormones gastric inhibitory peptide (GIP) and glucagon-like peptide-1 were not altered with prior exercise. However, prior exercise lowered IL-6 and GIP receptor mRNA (P<0.05) in subcutaneous adipose tissue. These data demonstrate that exercise altered multiple tissues that are involved in the postprandial metabolism of a novel OFTT.